Put the flank steak in a large glass dish. Moisten with the marinade. Cover with plastic wrap and refrigerate for 4-8 hours. Flip the meat a few times during the marinating process. Remove from fridge and drain surplus marinade into a bowl. Season all sides of the meat with Montreal steak spice and ground pepper.

Grill the steak on medium-high heat for 7-10 minutes or until desired doneness. (Should be eaten medium-rare) Baste the steaks with the remaining marinade during the cooking process.